1. Field of the Invention
The present invention relates to drill guides for accurately drilling a tunnel from the outer anterior surface of the tibia at a desired location distal to the tibial plateau upwardly through the tibia to exit at a desired location on the tibial plateau, and a method of using the drill guide for preselecting the length of the tunnel prior to any procedure which invades the bone. More specifically, the present invention relates to a tibial drill guide to facilitate an arthroscopic technique for replacing a deficient anterior cruciate ligament and a method for using the drill guide. The drill guide of the present invention includes provisions for preselecting a tibial tunnel length combined with the feature of a variable angle such that the preferred orientation of the tibial tunnel can always be achieved. In the preferred method for using the drill guide of the present invention, the preselected tunnel length is established on the drill guide and then the drill guide is manipulated to establish first the point on the tibial plateau at which the tunnel is to exit and then to vary the angle of the tunnel to find the point on the anterior medial surface of the tibia to start the drilling. Once these two points are established, with the preselected tibial tunnel length, the surgeon will know that the correct tunnel length will be achieved and that the angle of entry into the tibial plateau will be an appropriate angle.
2. The Prior Art
The prior art includes several different types of drill guides for forming tunnels in the tibia for anterior cruciate ligament replacement or enhancement. E. Marlowe Goble's U.S. Pat. No. 4,772,286 discloses a system for surgically implanting an allograft or prosthetic ligament as a replacement for a patient's cruciate ligaments. The '286 patent shows a tunnel 11 exiting the proximal tibia at a point 14 that is approximately two (2) centimeters posterior to the most anterior border of that tibial plateau 13. That point is said to be the approximate connection point of the end of the anterior cruciate ligament to the tibial bone surface. The '286 patent discloses at column 6 the use of a stainless steel guide wire to form an axis for the opening. The present invention provides a drill guide and a method for guiding the guide wire, known as a K-wire, while, at the same time, making sure that the length of the tunnel from the anterior surface of the tibia to the tibial plateau will be sufficient for the anchoring purpose desired.
The Dunbar U.S. Pat. No. 4,708,139 shows an arthroscopic drill guide, but the Dunbar guide does not have a device for preselecting the tunnel length.
Some commercial devices have a fixed angle of penetration relative to the tibial plateau such that the use of the device ends up with tunnels of uncontrolled length. Other commercial devices have fixed angles, but do have selectively variable drill sleeves to provide different tunnel lengths by choosing and installing different drill sleeves.
One commercial device has selectively variable angles with an arrangement for changing tunnel length, but there is no indicia means for rapidly establishing the preselected tunnel length. The maker of this type of device teaches setting the angle and then running up the drill sleeve until it hits bone. Thus, tunnel length is determined by the angle preselected and may vary each time.